From Texts to Executables

a series of debugging

Motivation

  • facing a bunch of bugs when I setup SDL2
  • kinds of write up

Background & Goal

Background - SDL2

  • Cross-platform software development library
  • Written in C
  • Allow you to write games  that can run on Linux, macOS, and Windows...

     
  • Similar to Allegro

Official libraries

  • SDL_image
  • SDL_mixer
  • SDL_net
  • SDL_ttf
  • SDL_rtf
     
  • What we need
    • SDL2, SDL2_image, SDL2_ttf, SDL2_gfx

Goal

  • Make the codes run on MacOS and Windows
     
  • Make the setup process easy
.
├── Makefile
├── fonts
│   └── ...
├── imgs
│   └── ...
├── maps
│   ├── ...
├── src
│   ├── constants.hpp
│   ├── game_utils.cpp
│   ├── game_utils.hpp
│   ├── main.cpp
│   ├── utils.cpp
│   ├── utils.hpp
│   ├── controllers
│   │   ├── ...
│   ├── views
│   │   ├── ...
│   ├── helpers
│   │   ├── ...
│   ├── models
│   │   ├── ...  
...

Run on MacOS

Brew Install + Make

brew install sdl2
brew install sdl2_image
brew install sdl2_ttf
brew install sdl2_gfx

make

But on Windows...

Cygwin

POSIX-compatible programming and runtime environment

directory layout that is similar to Unix-like systems
package system

Install Package

No SDL2_gfx

Make

Add the missing header files my solve the problem

Where should I put?

Let's talk about compiler first

  1. Preprocess
  2. Compile
  3. Assemble

Preprocess

  • Replace
    • # define ll long long
    • # include "foo.h"
// add.cpp
int add(int a, int b) {
	int result = a + b;
	return result;
#include "endBrace.h"
// endBrace.h
}

g++ -E -c add.cpp

Include Path

  • g++ --verbose -Iheader -c add.cpp

After adding header files

  1. compile successfully (generate object.o)
  2. linking error caused by missing files

Linker

What do linkers do

  • find functions & symbols then link them together
  • .o files -> executables
    • view.o, object.o, keyboard_controller.o, pacman.o...
    • -> main.exe

One kind of Linking error

// main.cpp
void Log(const char* message);

int main() {
    Log("hello world");
}
// log.cpp
#include <iostream>

void Logg(const char* message) {
    std::cout << message << std::endl;
}

If there's only 1 object file

  • linker is still needed
     
  • for example
    • tell c++ runtime library where’s the entry-point

Let's see our header files

#ifndef SDL_shape_h_
#define SDL_shape_h_

#include "SDL_stdinc.h" C++ */
#ifdef __cplusplus
extern "C" {
#endif

#define SDL_NONSHAPEABLE_WINDOW -1
#define SDL_INVALID_SHAPE_ARGUMENT -2
#define SDL_WINDOW_LACKS_SHAPE -3
extern DECLSPEC SDL_Window * SDLCALL SDL_CreateShapedWindow(
    const char *title,unsigned int x,unsigned int y,unsigned int w,
    unsigned int h,Uint32 flags);
...

header files are not enough, so related lib should be linked 

Library Path

  • -L<directory>

  • -lSDL2

    • find libSDL2

After adding related lib

Seem to work???

dll -> dynamic linking library

Then I use MinGW.

Static Linking & Dynamic Linking

Static Linking

  • copy all library modules into the final executable image
  • after linking, libraries are inside your exe file
  • need static library

Pros

  • usually faster

Cons

  • larger in size

Dynamic Linking

  • libraries are linked during runtime

  • need import library

Pros

  • smaller in size

Cons

  • usually slower

Where's dll

  1. The directory of the executable 

  2. The current directory

  3. The Windows system directory

  4. The Windows directory

  5. The directories listed in the PATH environment variable

But my code is

MinGW\bin\g++ .\src\utils.cpp -c -o bin\utils.o

.
├── Makefile
├── bin
│   └── main.exe
├── src
│   └── ...
├── MinGW
│   ├── bin
│   │   ├── g++.exe
│   │   ├── SDL2.dll
│   │   ├── ...
│   ├── lib
│   │   ├── libSDL2.a
│   │   ├── ...
│   ├── include
│   │   ├── SDL2
│   │       ├── SDL2_rotozoom
...

Full Picture

compile & assemble

Preprocess

libraries

(.lib)

.dll

include

lib

bin

  • bin for dll files
  • include for header files
  • lib for libraries
  • set up PATH environment in the batch file

Reference

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